Ruud Haak was the author of more than 30 dog books in Dutch, German, and English, and for over 40 years he was the editor-in-chief of the biggest Dutch dog magazine, Onze Hond (Our dog). Ruud travelled the world with his wife, Dr. Resi Gerritsen, teaching their unique methods to police departments, search-and-rescue organizations, and other dog trainers. He passed away in 2023.